The present invention relates to a record display medium using a smectic liquid crystal/polymer composite film, which is responsive to an electric field or heat to display or record various types of information, and use thereof. The record display medium of the present invention can be widely used as rewritable cards, displays, and other record display media.
At the present time, liquid crystals are applied as a display material to a variety of equipment and have been put to practical use in watches, clocks, pocket calculators, miniature televisions and the like. A nematic liquid crystal has been used for this purpose, and TN type and STN type display systems have been adopted.
This type of display device comprises a liquid crystal cell having a transparent electrode, a liquid crystal sealed thereinto, and a polarizing plate provided on both sides of the cell. The use of the polarizing plate results in a lowered angle of visibility and lack of brightness, necessitating a backlight having high power consumption. In addition, increasing the display area is difficult due to the necessity of making the cell thickness even, and there are additional problems such as a complicated structure and a high production cost.
In recent years, liquid crystal dispersion type devices using a liquid crystal/polymer composite film, wherein a liquid crystal is dispersed in a polymer matrix, have attracted attention as a liquid crystal display medium which can solve the above problems. Among them, those utilizing a smectic liquid crystal enable the liquid crystal to be maintained aligned even after removal of external energy used for alignment of the liquid crystal and hence have a memory effect, rendering these display devices useful as rewritable recording display media.
Not only a high contrast image but also such a high performance that causes neither lowering of the contrast nor disappearance of the displayed image in low temperature and high temperature regions is required of the rewritable recording display medium utilizing the smectic liquid crystal. At the present time, there is no record display medium which can satisfactorily meet this requirement.
Accordingly, an object of the present invention is to provide a record display medium that can display a high contrast image and is less likely to cause a lowering of contrast or disappearance of the displayed image even in low temperature and high temperature regions.